The field of the invention is synthetic resins from polyhydric alcohol-polycarboxylic acid reaction products. The invention is particularly related to a process for the manufacture of low pilling effect polyester fiber products.
The state of the art of the present invention may be ascertained by reference to the Kirk-Othmer "Encyclopedia of Chemical Technology", Vol. 16 (1968), pages 143-159, under the section entitled "Polyester Fibers"; U.S. Pat. No. 2,465,319 which shows the preparation of polyethylene terephthalate; U.S. Pat. No. 3,391,123 of Stedley, which issued July 2, 1968 and shows the state of the art of improving the pilling effect of polyethylene and shows the state of the art of improving the pilling effect of polyethylene terephthalate textile fibers; the Herman Mark et al "Encyclopedia of Polymer Science and Technology", Vol. 1 (1964) under the section "Acids, Maleic and Fumaric", pp. 67-95, particularly pp. 76-84 concerning copolymerization, Vol. 1 (1964) under the section "Acrylic Acid Polymers", pp. 197-226, particularly pp. 204-206 concerning copolymerization, Vol. 1 (1964) under the section "Acrylic Ester Polymers", particularly pages 263 and 264, and Vol. 14 (1971) under the section "Vinyl Alcohol Polymers", pp. 149-234, particularly p. 180 concerning copolymerization preferred for use in the present invention, the disclosures of which are incorporated herein.
On account of the great many outstanding properties such as high melting point, resistance to chemicals, heat, hot water and light, and because of their mechanical properties, yarns and fibers made from polyethylene terephthalate have achieved large significance in the textile and garment industries.
However, besides their numerous advantages, polyester fibers also suffer from drawbacks. One of these is the so-called pilling effect. It is caused by fibers being pulled out of the fabric during wear and twisting into small spheres firmly anchored in the fabric. The fabric surface thereby assumes an unpleasant appearance, and the quality of the garments is thereby degraded.
There have been many attempts to remedy this drawback of the polyesters by a variety of measures. The most frequently applied method consists in decreasing the polyester molecular weight and in thus obtaining correspondingly reduced relative specific viscosities (hereafter abbreviated as RSV) of about 0.35 to 0.45 dl/gm (deciliters per gram as measured at a concentration of 0.23 g in 100 ml phenol tetrachloroethane 60/40 at 25.degree. C), whereby one obtains lesser yarn strength as disclosed in Japanese Application No. 24, 932/65. However, appreciably difficulties are caused when such material is melt spun, because of the very low viscosity of the melt.
Another possibility of preparing low pilling polyesters comprises the use of monomerous compounds with three or more functional groups, for instance such polyols as glycerin, such polyacids as trimesic acid, such polyphenols as phloroglucine, or such amino compounds as diethanolamine, as disclosed in German Offenlegungschrift No. 1,928,436. Partially branched polyester fibers are obtained in this manner, which compared with their molecular weight, are of higher melt viscosity than is the case for substantially linear products.
Again, repeated attempts were made to post-facto chemically degrade polyester fibers and fabrics made therefrom, by treating them at elevated temperatures with water, soda, ammonium, hydrazine, amines, carboxylic acids or alcohols, as disclosed in Czech Pat. No. 108,689; Dutch Pat. No. 91, 330; French Pat. No. 1,551,050; Japanese Pat. No. 7,122,174; and German Auslegeschrift No. 1,024,482. It was found, however, that such degradation can be controlled only with difficulty and is difficult to reproduce. In many instances attempts were made to generate weak spots in the molecule, which also may lead to branching or reticulation, by building in chain links with hetero-atoms, especially silicon, as disclosed in U.S. Pat. No. 3,335,211, and German Auslegeschrift No. 1,273,123, with boron, as disclosed in U.S. Pat. No. 3,391,123 and German Auslegeschrift No. 1,469,127, or with aluminum, as disclosed in German Offenlegungschrift No. 1,545,039, with hydrolytic dissociation subsequently being feasible at these weak spots. In this process too there is difficulty in reproducing the results. It is furthermore necessary to operate in entirely non-aqueous manner up to the time of hydrolytic dissociation and it is generally known that this will cause particular difficulties.
Thus, the known processes are not satisfactory in every respect.